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• Posted February 11, 2026

Obesity Linked To 1 In 4 Infectious Disease Deaths In U.S.

Obesity contributes to about 1 in every 4 infectious disease deaths in the United States, the most among wealthy countries, a major new study estimates.

People with obesity have a higher risk of hospitalization or death from infectious diseases ranging from influenza and COVID-19 to stomach flu and urinary tract infections, researchers reported Feb. 9 in the journal The Lancet.

Further, the risk rises with a person’s weight. Those with the highest levels of obesity have three times the risk from infectious diseases, researchers found.

Overall, obesity is linked to about 1 in every 10 infection-related deaths worldwide, researchers concluded.

“People living with obesity are significantly more likely to become severely ill or to die from a wide range of infectious diseases,” said lead researcher Solja Nyberg, a bioinformatician at the University of Helsinki in Finland.

“As obesity rates are expected to rise globally, so will the number of deaths and hospitalizations from infectious diseases linked to obesity,” Nyberg added in a news release.

For the new study, researchers pooled data from two Finnish studies and one U.K. health research project, including more than 540,000 people all told.

People were followed for an average of 13 to 14 years, and their body mass index (BMI) used to compare obesity to risk of serious infections. BMI is an estimate of body fat based on height and weight.

Results showed that people with obesity — defined as a BMI as 30 or more — had a 70% higher risk of hospitalization or death from any infectious disease, compared to those with a healthy BMI of 18.5 to 24.9.

This risk increased steadily as body weight rose, researchers found. People with severe obesity of 40 or more had three times the risk of people at a healthy weight.

“Obesity affects more than just the chronic diseases that we normally focus on, such as diabetes and hypertension and heart disease," said Dr. Andrew Bates, director of minimally invasive surgery at South Shore University Hospital, Northwell Health in Bayshore, New York.

"This was showing a very clear linear association between various and increasing levels of obesity and the risk of infections, serious infections and fatal infections, which directly contributed to about 10% of the infection-related deaths worldwide every year,” added Bates, who reviewed the findings.

Researchers also looked at people’s risk of 10 common infectious disease, and for most they found a greater risk among people with obesity.

These diseases include flu, COVID, pneumonia, gastroenteritis, urinary tract infections and lower respiratory tract infections.

However, the study found no link between obesity and increased risk from HIV or tuberculosis.

There are a number of potential explanations why obesity might increase risk of infections, researchers said.

“It is plausible that obesity weakens the immune system’s ability to defend against the infectious bacteria, viruses, parasites or fungi, therefore resulting in more serious diseases,” said senior researcher Mika Kivimaki, chair of social epidemiology at University College London.

“Evidence from trials of GLP-1 weight-loss drugs fits with this, as reducing obesity also appears to lower the risk of severe infections, alongside many other health benefits,” Kivimaki said in a news release. “That said, additional research is required to confirm the mechanisms underlying these associations.”

More information

The U.S. Centers for Disease Control and Prevention has more on how obesity affects health.

SOURCES: The Lancet, news release, Feb. 9, 2026; Dr. Andrew Bates, director of minimally invasive surgery, South Shore University Hospital, Northwell Health, Bayshore, New York